![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/1_0.png.webp?h=bfced127&itok=QmUBieeo)#### Raw Water Blending and Powdered Activated Carbon Raw Water Blending and Powdered Activated Carbon [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/1_0.png.webp?h=bfced127&itok=wpIqMnT2 "Raw Water Blending and Powdered Activated Carbon") Water from two sources can potentially be utilised for production. These are secondary treated wastewater from Gammams Water Care Works and water of the Goreangab Dam. Either water source or a mixture of the two could be used for the reclamation of potable water. Since 2008 the sole supply of raw water is secondary effluent. Powdered activated carbon can be added to the raw water for the removal of dissolved organic compounds. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/2_1_0.png.webp?h=bfced127&itok=fp_U2DLF)#### Preoxidation and Coagulation Preoxidation and Coagulation [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/2_1_0.png.webp?h=bfced127&itok=Uwnss8Qo "Preoxidation and Coagulation ") Ozone (O3) is added to the raw water; after preozonation, potassium permanganate (KmnO4) is added to precipitate dissolved manganese (Mn2+) followed by addition of the coagulant ferric chloride (FeCl3), which causes the destabilisation of particles and formation of micro-flocs (coagulation process). ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/3_0.png.webp?h=bfced127&itok=hztlNNnD)#### Flocculation Flocculation [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/3_0.png.webp?h=bfced127&itok=M6NAW75f "Flocculation") After the coagulation the water is stirred very slowly to enable the micro-flow to grow into larger floc. To assist this flocculation process a polymer could be added if needed. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/4_0.png.webp?h=bfced127&itok=uoy3sQGB)#### Dissolved Air Flotation Dissolved Air Flotation [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/4_0.png.webp?h=bfced127&itok=KxYWppwh "Dissolved Air Flotation") After formation of the flocs, they need to be separated from the water. Microscopic air bubbles are formed (water being super saturated with air) and mixed with the flocculated water, the air bubbles will attach to the flocs resulting in rising them to the surface of the water. This will form a scum layer on top of the water, which is periodically removed. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/5_0.png.webp?h=bfced127&itok=-9jCNNKb)#### Rapid Gravity Filtration Rapid Gravity Filtration [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/5_0.png.webp?h=bfced127&itok=d5Wt0xoH "Rapid Gravity Filtration") Prior to the dual media filtration caustic soda (NaOH) for pH stabilisation and potassium permanganate (KmnO4) for iron and manganese precipitation and subsequent removal thereof on the filter beds is added. The main function of the dual media filters (anthracite and sand) is to remove suspended particles, which were not removed with the dissolved air flotation. The sand filters are periodically backwashed. The backwash water together with the scum of the dissolved air flotation is further treated at the Otjomuise effluent treatment works. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/6_0.png.webp?h=bfced127&itok=407rLhIH)#### Ozonation Ozonation [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/6_0.png.webp?h=bfced127&itok=-nDKn0En "Ozonation") Ozone (O3) is a very powerful oxidant and disinfectant. The gas is produced onsite from high purity oxygen (92 – 95% purity), which also is produced onsite. The ozone gas is injected into the filtered water to oxidise dissolved organic compounds to biodegradable compounds and for the disinfection of the water; all remaining viruses, bacteria and parasites (like Giardia and Cryptosporidium). The oxidised organic compounds (this includes pharmaceuticals) are then available for further biological degradation. The remaining ozone is degraded by the addition of hydrogen peroxide (H2O2). ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/7_0.png.webp?h=bfced127&itok=jf4Fls2-)#### Biological Activated Carbon Filtration (BAC) Biological Activated Carbon Filtration (BAC) [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/7_0.png.webp?h=bfced127&itok=DsQzAyOF "Biological Activated Carbon Filtration (BAC)") Granular activated carbon provides an ideal surface area for the growth of microorganisms. The biodegradable dissolved organic compounds (after the ozonation) are removed by the microorganisms living on the surface of the carbon as the water passes through the filter beds. These filters periodically backwashed. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/8_0.png.webp?h=bfced127&itok=9lzOtHsZ)#### Granular Activated Carbon Filtration (GAC) Granular Activated Carbon Filtration (GAC) [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/8_0.png.webp?h=bfced127&itok=o5XcoW89 "Granular Activated Carbon Filtration (GAC)") The remaining dissolved organic compounds are absorbed onto granular activated carbon. The removal of dissolved organic carbon is important to prevent the formation of disinfection byproducts and to prevent the recycling of pharmaceuticals, which could be detrimental to human health. Also these filters are backwashed periodically. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/9_0.png.webp?h=bfced127&itok=lbimcfxA)#### Ulftrafiltration Ulftrafiltration [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/9_0.png.webp?h=bfced127&itok=ImzTzwIh "Ulftrafiltration") Ultrafiltration membranes are used as the final polishing step for the removal of all remaining suspended particles and microorganisms and viruses. The membranes are cleaned and sterilised regulalry. ![](/sites/g/files/dvc3321/files/styles/gallery_thumbnail/public/image/2018/03/10_0.png.webp?h=bfced127&itok=8I9Q7fB0)#### Disinfection and Stabilisation Disinfection and Stabilisation [](#) ![](/sites/g/files/dvc3321/files/styles/gallery_popup/public/image/2018/03/10_0.png.webp?h=bfced127&itok=4BSeelB6 "Disinfection and Stabilisation") The final product water (the filtrate of the ultrafiltration) is prepared for blending with other potable water sources by adding chlorine (Cl2) for disinfection and caustic soda (NaOH) for pH adjustment. In order to prevent any health risk to the consumer, chlorine is added to the final water for protection during the distribution. The potable water produced by Wingoc conforms to the highest quality standards and guidelines. The water is pumped to the New Western Pump Station where it is mixed with other potable water sources and distributed by the City of Windhoek to the consumers.